At a glance
～までだ means "I'll just ~" (a calm decision when plan A fails) or "I only did ~, nothing more" (modesty or justification). It is a formal N1 expression.
Verb (dictionary form) + までだ "I'll just ~"
Verb (た-form) + までだ "I only did ~"
バスがないなら、歩いて帰るまでだ。 If there's no bus, I'll just walk home.
How to form it
までだ attaches to verbs. The verb form decides the meaning:
| Verb group | Dictionary form: "I'll just ~" | た-form: "I only did ~" |
|---|---|---|
| う-verb | 書くまでだ | 書いたまでだ |
| る-verb | 食べるまでだ | 食べたまでだ |
| する | するまでだ | したまでだ |
| 来る | 来るまでだ | 来たまでだ |
| Register | Form |
|---|---|
| Plain | までだ／までのことだ |
| Polite | までです／までのことです |